Roy Surratt escapes from a prison chain gang. It's part of a plan he set up with his former cellmate, Joe Venci. They're to meet later, but when Roy arrives at the appointed place, Joe's wife is there. Joe is dead, and his wife wants Roy to kill someone for her. Roy figures out that Joe was blackmailing the town's prominent citizens, so he decides to take over.
Roy regards himself as a philosopher and prides himself on his IQ (149) and his superiority to everyone around him. You know where this is going, already, don't you? One of the blackmail schemes go awry. Roy meets another woman, Pat Kelso, and falls for her, but Joe's wife is still after him because he understands her needs. They're different needs, for sure, and the kinkiness of their encounters is pretty startling. Think The Killer Inside Me, and you won't be far wrong.
Things fall apart, and Roy goes on the run. He also makes a number of blunders, and he finds out that maybe his supposedly superior brain hasn't allowed him to fool as many people as he thought. It doesn't end well for him, but that's not a spoiler. You knew it wouldn't.